1. Field of the Invention
This invention relates to a process and apparatus for photographically enlarging and developing an image.
2. Description of the Prior Art
It is known photographically to reproduce an image by advancing image receptive material from a roll of such material to an image receiving location, projecting the image on to the material at such location and subsequently treating the imaged material to fix the image therein.
One such known apparatus is disclosed in U.K. patent specification No. 1,182,303 in which the material is a photosensitive sheet advanced from a roll of such material to a substantially vertical image receiving position. The material is advanced to the image receiving location from the roll by feed rolls disposed between the roll of material and the imaging receiving location, i.e., upstream of such location. In order to support the advanced material at the image receiving location it is advanced between a planar rear support plate and a transparent plate which retain the material between them at the image receiving location. The transparent plate clearly has to be free of imperfections and markings to transmit the image to the material. Following exposure, the exposed section of the photosensitive sheet is advanced upwardly between a rotary knife and anvil. The knife operates by rotation to sever the sheet to separate the exposed portion from the remainder. The exposed section of the photosensitive sheet is then advanced through a processing section in which processing liquid is applied to the exposed face of the sheet to produce a silver transfer layer on the surface of a translucent layer.
A further known form of apparatus is disclosed in U.K. patent specification No. 1,201,346 in which photosensitive material is advanced from a cassette roll of such material to a substantially horizontal imaging platen 2 which defines the imaging plane. The material is advanced from the cassette roll to the imaging platen by drive rolls located adjacent the cassette roll and between the latter and the imaging platen, i.e., upstream of the horizontal image receiving location. Cutting means is provided adjacent the cassette roll, i.e., upstream of the image receiving location to sever the exposed sheet from the roll after exposure and the severed sheet and exposed sheet is advanced to a processing location.
Another form of known apparatus is disclosed in U.K. patent specification No. 1,436,631 for electrophotographic colour copying. Paper is supplied from a roll and, after being cut into size by a cutter, is maintained horizontal at the exposure position on a transport belt means. The paper is advanced to the exposure position by feed rollers disposed between such position and the roll, i.e., upstream of the exposure position and the cutter which is also upstream of the exposure position severs the material before exposure. The paper at the exposure position is changed uniformly and then exposed to light. A developing unit moves horizontally over the paper to develop an image corresponding to the latent charged image with a first colour toner. This is repeated according to the number of colours required. The copy thus produced is then delivered to an outlet.
There is also known from U.K. patent specification published under No. 2002131A a microfilm processor for photographically recording an image on microfilm. In this apparatus, the film is advanced from a roll of film to a horizontal image receiving position by rollers disposed upstream of such position, i.e., between the image receiving location and the roll. A rotary cutter is provided adjacent to such location and operates to sever the film after a predetermined number of frames have been advanced to the image receiving location, whether or not all such frames have been exposed. The severed film is then advanced for processing.
None of the known arrangements is concerned with producing an enlarged image but in each case the material is advanced from a roll of such material by feed rollers disposed between the roll of material and the image receiving location i.e., upstream of the image receiving location so that the material is effectively pushed to that location. Such an arrangement has the disadvantage that the material is not fed under tension nor is it held under tension at the image receiving location. Such a disadvantage may not be too onerous in apparatus, such as the last three known arrangements referred to above, in which the material is supported horizontally at the image receiving location. However, such an arrangement is wasteful of floor space in apparatus intended to produce, as in the present case, an enlarged image which could be of poster size.
Only U.K. patent specification No. 1,182,303 discloses a substantially vertical image receiving position and seeks to overcome the disadvantage referred to by supporting the material at the image receiving location between a rear support plate and a front transparent window. However, apart from the disadvantages of the window, the material at the image receiving location is not in tension and, as it has to be pushed between the window and the support flat some compromise must be made between the conflicting requirements of on the one hand providing sufficient spacing between the support plate and the window to avoid or minimise friction between the material with its sensitive surface and the plate and window and, on the other hand, making this spacing sufficiently small to avoid undue sagging of the material under its own weight.